It has long been recognized that the heart performs its filling and emptying as a consequence of alteration of its wall executing a complete cycle during each heartbeat. On general physical considerations, universally applicable, these parameters can be identified as inertance, resistance and compliance. Ultimately, the process which permits these parameters to execute cycle changes is defined by the capability of the pump's muscle to generate (convert), store, and release (convert) energy, Hence, it stands to reason that the time-varying parameters are coupled to the energy transformation processes; dysfunction of the latter will make the former abnormal. Knowledge of the time-varying parameters offers two fundamental features: 1) by defining the pump properties it provides the only currently known avenue to understanding the interaction between the function of the heart and the arterial and venous vascular systems; 2) it provides a quantitative approach to characterize the energy process. Both have obvious clinical implications. This proposal focuses on the determination of the three time-varying parameters utilizing experimental and analytical techniques. Two fundamentally different techniques are now available to achieve this goal, one of which requires system perturbation.